OBD2 datastream - lt fuel trim - +25% - ideas??

Good evening,

I was wondering if anyone might have an idea as to why my long term fuel
trim in high (+25% usually). This causes a minor nuisance at startup but
otherwise I have no perfrormance or drivability issues to speak of. My fuel
economy has never been worse though.

Here's the data...

RPM 751 (verified ok)
Ign Timing Advance -8.5d
Intake Air Temp- 12C
TPS - 1%
O2 bank 1 - 0.040 (switches to .8-.9 with no issues)
O2 bank 2- 0.275 (seems slow to switch - maybe this is the issue?)
Load value - 3.1%
Long Term Fuel Trim- 25%
MAP Sensor- 39 kPa
Coolant Temp- 93C

The vehicle is a 95 GMC JimmySLT 4x4

Does the MAP and Timing info seem ok?

Thanks.
Andrew.

it would help some of us if the readings were in english not metric,
thanks


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in article , J-Mech at
wrote on 2/24/07 11:31 PM:

>
> it would help some of us if the readings were in english not metric,
> thanks
>
Ok..

Here's the data... Is this better??

RPM 751 (verified ok)
Ign Timing Advance: -8.5d
Intake Air Temp: 53.6d F
TPS: 1%
O2 bank 1: 0.040VDC (switches to .8-.9 with no issues)
O2 bank 2: 0.275VDC (seems slow to switch - maybe this is the issue?)
Load value: 3.1%
Long Term Fuel Trim: +25%
MAP Sensor: 11.51 inHg (.39BAR)
Coolant Temp: 199.4d F

The vehicle is a 95 GMC JimmySLT 4x4

Does the MAP and Timing info seem ok?

Thanks.
Andrew.

hey Andrew-no service engine soon lite other than initial key on lite
check?



On Feb 24, 11:31 pm, J-Mech > wrote:
> it would help some of us if the readings were in english not metric,
> thanks
>
> --
> J-Mech
> ------------------------------------------------------------------------
> J-Mech's Profile:http://www.automotiveforums.com/vbul...?userid=496273
> View this thread:http://www.automotiveforums.com/vbul...d.php?t=677902
>
> http://www.automotiveforums.com

In article >,
AWN > wrote:

> in article , J-Mech at
> wrote on 2/24/07 11:31 PM:
>
> >
> > it would help some of us if the readings were in english not metric,
> > thanks
> >
> Ok..
>
> Here's the data... Is this better??
>
> RPM 751 (verified ok)
> Ign Timing Advance: -8.5d
> Intake Air Temp: 53.6d F
> TPS: 1%
> O2 bank 1: 0.040VDC (switches to .8-.9 with no issues)
> O2 bank 2: 0.275VDC (seems slow to switch - maybe this is the issue?)
> Load value: 3.1%
> Long Term Fuel Trim: +25%
> MAP Sensor: 11.51 inHg (.39BAR)
> Coolant Temp: 199.4d F
>
> The vehicle is a 95 GMC JimmySLT 4x4
>
> Does the MAP and Timing info seem ok?

It might be. Without a BARO reading, it is impossible to tell.

What is the short term fuel trim?

What are the long and short term fuel trims for the other bank?

What is the Mass Air Flow reading?

What happens to the readings during cruise?

Taken at face value, the +25% fuel trim indicates a lean
condition. This can be caused by vacuum leaks, plugged injector
poppets, low fuel pressure, wrong PCV valve, skewed MAF sensor,
skewed O2 sensors, air leaks in the exhaust system ahead of the
O2 sensors...

Jerry,

No CEL or codes. No.
Thanks.
Andrew.




in article , blazerman
at wrote on 2/25/07 9:20 AM:

> hey Andrew-no service engine soon lite other than initial key on lite
> check?

Andrew-does your scantool give you any fuel trim counts, ex.- 128
counts-above(higher or lower)? jerry @peru-motors.com ps also wonder
if your EGR valve could be slightly/ partially open-not going
completely closed due to carbon build up over time thus causing your
hard start. Just a guess


On Feb 25, 12:47 pm, AWN > wrote:
> Jerry,
>
> No CEL or codes. No.
> Thanks.
> Andrew.
>
> in article om, blazerman
> at wrote on 2/25/07 9:20 AM:
>
> > hey Andrew-no service engine soon lite other than initial key on lite
> > check?

In article
. com>,
"blazerman" > wrote:

> Andrew-does your scantool give you any fuel trim counts, ex.- 128

Read the subject line.

your 11.51 InHg looks like you have a vac leakit should be about 8- 10


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Thanks J-Mech.
Do you think a vac leak would lead to a 25% adjustment in long term fuel
trim? I just finished checking every hose and gasket (water tested also)
and I can't find a leak. I did have a partial crack on the vac reservoir
though but I don't think it was serious enough to cause such a wide swing.
I will rescan and get back if there's any change. I don't have any hard
start issues any longer but the fuel trim starts at about +7 and tops out at
25 over after maybe 2 minutes of idling.
A suggestion had been made that a top end motovac treatment might be the
ticket? Any thoughts on this?

Thanks again!
Andrew.






in article , J-Mech at
wrote on 2/25/07 8:00 PM:

> your 11.51 InHg looks like you have a vac leakit should be about 8- 10
>
>
> --
> J-Mech